The present invention relates to a method of manufacturing a multi dimensional transducer using multi-layer transducer ceramic. In particular, a method of manufacturing 1.25D, 1.5D, 1.75D and two-dimensional arrays with elements using multi-layer ceramic.
Multi-dimensional ultrasound arrays provide a large number of elements, which require a great number of electrical connections to the system. For multi-layer elements, an additional electrical connection within the element is required. Additional electrical connections are difficult for multi dimensional arrays. For a linear array, the electrodes of the various layers are easily accessible for sputtering to provide electrical interconnection to the system. For multi-dimensional arrays, the internal electrodes for elements internal to the array are not accessible. Furthermore, since the size of the element is significantly reduced compared to a conventional transducer, material imperfections or minor processing mistakes can render an element useless.
U.S. Pat. No. 5,548,564 discloses forming vias at the edges of elements for making signal and ground connections to various electrodes in a multi-layer element. Vias may be 50 to 150 micrometers in diameter or larger. Due to the fine pitch of two-dimensional or multi-dimensional array elements, such as 310 micrometers, the large vias limit the element size and deteriorate the performance of each element. One via may be shared along four elements to make ground and signal connections, but precise and accurate placement of the vias in alignment with the transducer material layers is difficult. The vias also waste transducer material. Using separate vias for signal connections and ground connections to avoid short circuiting may allow for very little variation or tolerance for the placement and size of the vias.
U.S. Pat. No. 5,834,880 uses high aspect ratio sputtering on the multi-layer elements of the multi dimensional array. To achieve reliable electrical connection to the internal layers, high aspect ratio sputtering may require an increased kerf width. Electrode material is sputtered within the kerfs for interconnecting electrodes from various layers. The sputtering is done for a front and back or top and bottom of the array separately, increasing the amount of handling of the transducer array. Increased handling may lead to decreased array performance. To allow the high aspect ratio sputtering, dicing cuts forming the kerfs are made through most but not all of the transducer material. The transducer material bridges between the elements weekly maintains interconnection of the array. Handling may break the connections, ruining the array. Dicing is also required to electrically separate the connections.
The present invention is defined by the following claims, and nothing in this section should be taken as limitation on those claims. By way of introduction, the preferred embodiments described below include a method of manufacturing multiple dimension transducer arrays of multiple layer elements. A plurality of multiple layer strips or modules are formed. The strips are separate, such as an elongated strip corresponding in size to one row of elements. Interconnections between the electrodes of various layers or separate connections from the various electrodes to a bottom of the strip are formed on the separate multiple layer strips. The separate strips are then aligned within a frame and bonded together. The resulting sheet of multiple layer transducer material is then diced to form elements. Due to the previous interconnection of electrodes, each element includes electrical connections for each of the layer electrodes, avoiding the need for vias or high aspect ratio sputtering.
Further aspects and advantages of this modular approach of the invention are discussed below in conjunction with the preferred embodiments.